Air source heat pump zoning hot gas bypass defrosting method and technology thereof

Abstract

This invention proposes a zoned hot gas bypass defrosting method and technology for air source heat pumps. Its key feature is that the air source heat pump evaporator is divided into two sections for sequential defrosting. The "zoned hot gas defrosting circuit and its control system" of this invention is added to one or two air source heat pump refrigerant circulation circuits to achieve alternating defrosting and heat absorption by the first and second zone evaporators. The zoned hot gas defrosting circuit consists of two four-way valves, a defrosting hot gas inlet pipe with a one-way valve connected between them, a throttling bypass, and a bidirectional throttling device between the two evaporators. The first four-way valve handles compressor exhaust defrosting or normal heating / cooling modes, as well as switching the connection and disconnection of the throttling bypass. The second four-way valve handles the defrosting modes of the first and second evaporators and, in conjunction with the heat pump's third four-way valve, completes the switching between normal heating and cooling modes. The structure and control are simple, highly versatile, and can be connected to various types of air source heat pumps. The defrosting heat mainly comes from the air, resulting in energy savings.

Description

Technical Field

[0001] This invention relates to the fields of energy saving and heat pump air conditioning, specifically defrosting technology for air source heat pumps. Background Technology

[0002] Air source heat pumps extract heat energy from the air to produce domestic hot water and heating, which can significantly reduce the consumption of high-grade electricity and gas, and are therefore widely used as energy-saving products. However, air source heat pumps have a major drawback: in cold and damp winter weather, frost forms on the evaporator coil fins. As the frost layer thickens, airflow resistance increases, reducing the airflow through the evaporator and drastically decreasing heat exchange efficiency. This worsens the already low performance of the heat pump in winter, making defrosting essential; otherwise, the air source heat pump becomes unusable. While decades of research have yielded various defrosting methods for air source heat pumps—including refrigerant reverse circulation defrosting, hot gas bypass defrosting, and a combination of heat storage and hot gas bypass—the problem of wasting high-grade electrical energy on defrosting remains unresolved. This is because the source of inexpensive energy for defrosting remains unsolved, relying primarily on compressor input power. My own patent, "Defrosting Method for Air Source Heat Pump Water Heaters," is numbered ZL 201510180387.8 (application date: May 2015).17) introduces several defrosting methods and proposes a defrosting method using hot water from a hot water storage tank. This is an external heat defrosting method. Since external heat is only effective for heat pumps that use hot water and requires an external water circuit and circulation pump, it has not been widely adopted. The principles, advantages and disadvantages of current defrosting methods are simply analyzed as follows: (1) Refrigerant reverse circulation defrosting method: During defrosting, the four-way valve of the heat pump refrigerant circulation loop is switched, and the refrigerant circulates in reverse (refrigeration cycle). The evaporator that was originally frosted becomes a condenser. The compressor exhaust enters the frosted evaporator, and the refrigerant condenses and releases heat to defrost. The defrosting speed is relatively fast; however, during reverse circulation defrosting, the refrigerant must absorb heat from the original hot water tank or the heated room, otherwise reverse circulation cannot proceed. This inevitably causes the hot water heat exchanger to output cold water, and the hot water temperature will drop sharply from 45℃ to about 7℃, or cold air will be blown into the heated room. To reduce this situation, the indoor fan speed is reduced very low when heating the room. This, in turn, causes the circulating refrigerant to absorb only a small amount of heat, resulting in low refrigerant evaporation, low compressor suction volume, low compressor discharge pressure, and low compressor input power. The compressor's input power is an important source of defrosting, and a reduction in input power will prolong the defrosting time; the second disadvantage is that the system pressure fluctuates greatly when the system is switched, and the system management is greatly impacted. In order to mitigate its harm, it is necessary to set the shutdown time for the switching operation, which is generally 2-3 minutes. However, switching back and forth requires re-establishing stable operation, which reduces the normal heating time of the heat pump and consumes a lot of defrosting energy; in addition, it will also cause the "oil run" problem; (2) Hot gas bypass defrosting mode, theoretically designed to lead the compressor exhaust port to the evaporator of the coil fins for defrosting, is more effective than reverse circulation defrosting. The problem is that the initial hot air introduced into the frosted evaporator is condensed into liquid. Since the condensate requires heat to vaporize, and the evaporator has no heat absorption function during defrosting, a significant portion of the compressor's exhaust must be bypassed and directly routed to the gas-liquid separator to evaporate the refrigerant liquid produced during defrosting in order to maintain the refrigerant compression cycle. Because there is no heat source for defrosting, the energy required for defrosting is essentially all electrical work input to the compressor. Furthermore, even if hot air flows back to the gas-liquid separator during defrosting, the compressor's intake pressure remains very low; experiments have shown that the average exhaust pressure is only about 1.20-1.30 MPa, the compressor's input power is less than 1 / 3 of the normal value, and the compressor's input power is also very small, so the defrosting time is too long. Although the hot gas bypass defrosting method overcomes the "oil run" problem of reverse circulation defrosting and reduces the impact of the defrosting process on the system, it has not been adopted in practice because there is no cheap heat source for defrosting; (3) Energy storage defrosting compared with the hot gas bypass defrosting mode. In order to solve the problem of no heat source in the hot gas bypass defrosting method, a method combining energy storage defrosting and hot gas bypass is proposed. Its principle is to add a condenser outlet in the refrigerant circulation loop. A phase change heat exchanger consists of heating heat exchange tubes and a heat extraction heat exchanger, filled with a solid-liquid phase change material. The heating heat exchange tubes are connected to the high-temperature refrigerant liquid at the condenser outlet of the refrigerant heat pump cycle or to the compressor discharge line, while the heat extraction heat exchange tubes are connected to the compressor suction line. To ensure sufficient heat storage for defrosting, a sufficient amount of phase change material is required. During normal circulation, the compressor suction cannot pass through the heat extraction heat exchange tubes; otherwise, the phase change heat exchanger will not have the heat required for defrosting. During defrosting, the evaporator outlet must be filled with solid-liquid phase change material. The refrigerant passes through the heat exchange tubes at the outlet, and the refrigerant must be separated from the heat exchange tubes at the end of defrosting, making the system complex. Crucially, the phase change medium in phase change heat exchangers has poor heat storage performance. Phase change heat exchangers must have sufficient heat storage capacity for defrosting and a sufficient heat transfer rate; all these problems have not been well solved. Therefore, the application of energy storage thermal gas bypass defrosting methods is almost non-existent in air source heat pump water heaters and heating systems on the market. The applicant previously proposed a hot water spray defrosting method using a hot water tank, but this requires the addition of an external spray water system. In winter, there are also issues with preventing water pipes from freezing and clogging, and dealing with hot water drains from sprinklers, which have hindered their widespread adoption. All current heat pump defrosting methods are ineffective because the heat pump loses its ability to absorb heat from the ambient air during defrosting. There is no cheap energy source for defrosting, and the compressor operates under low pressure, resulting in low compressor input power and a lengthy defrosting process relying on compressor input power. In contrast, the currently used reverse circulation defrosting method can still draw some heat from the heating source for defrosting, although customers are dissatisfied, it is a necessary compromise. Summary of the Invention

[0003] To overcome the shortcomings of existing air source heat pump defrosting methods, this invention proposes an innovative defrosting method, namely the "Air Source Heat Pump Zoned Hot Gas Bypass Defrosting Method and Technology." Its defrosting principle is as follows: evaporator defrosting is performed in zones, either by dividing the evaporator into two zones or by having two air source heat pumps mutually assist in defrosting and then jointly provide heating. While the first evaporator in zone one is defrosting, the second evaporator in zone two continues to operate. After the first evaporator finishes defrosting, the second evaporator begins defrosting, and the first evaporator resumes normal operation. The defrosting hot gas comes from the high-temperature exhaust gas from the self-contained compressor, and the heat in the exhaust gas comes from the heat absorbed from the ambient air by the normally operating evaporator and the power input from the compressor. Due to the zoned hot gas bypass defrosting method of this invention… During defrosting, the heat from the refrigerant evaporation in the evaporator is drawn from the ambient air. All the refrigerant condensate evaporates during defrosting, resulting in high compressor intake pressure, large intake volume, high compressor input power, and higher discharge pressure and temperature, leading to faster defrosting. Furthermore, the refrigerant circulation direction of the heat pump remains unchanged, causing no impact on the equipment and preventing oil leakage. The equipment can operate stably after defrosting, shortening the defrosting time and relatively increasing equipment output. This invention overcomes almost all the shortcomings of existing defrosting methods. Its technology involves adding a zoned hot gas defrosting circuit and its control system to the refrigerant circulation circuit of the air source heat pump to achieve alternating defrosting of the two evaporators and ensure the normal operation of the heat pump's original cooling and heating functions.

[0004] Technical solution of the present invention

[0005] A zoned hot gas bypass defrosting method and technology for air source heat pumps, wherein the air source heat pumps include: a single-function air source heat pump for heating, a dual-function air source heat pump for cooling and heating, a triple-function air source heat pump for cooling, heating, and hot water, and an air source water source heat pump water heater; the refrigerant circulation loop of the above four types of air source heat pumps includes basic components such as: compressor, condenser, expansion valve, evaporator, gas-liquid separator, and one-way valve; the condenser is equipped with a water pump or fan; the evaporator is a finned coil air heat exchanger equipped with a fan; the evaporator is a water heat exchanger equipped with a wastewater pump; the dual-function air source heat pump for cooling and heating also includes a four-way valve; the air source heat pump for cooling and heating... The three-in-one hot water heater also includes a four-way valve, a three-way valve, and a domestic hot water heat exchanger. Its characteristic is that the air source heat pump zoned hot gas bypass defrosting method and technology involves modifying and adding a zoned hot gas defrosting circuit and its control system to the refrigerant circulation loop of the aforementioned four types of air source heat pumps. The principle of the zoned hot gas bypass defrosting method is as follows: the evaporator of the air source heat pump is divided into two zones, referred to as the first and second evaporators respectively. Bypass hot gas is used for zoned defrosting sequentially, i.e., the first and second evaporators are defrosted sequentially. The first evaporator of the air source / water source heat pump water heater is a wind evaporator, and the second evaporator is a water evaporator. For defrosting, the first evaporator uses a second water evaporator to absorb heat. During defrosting, the compressor exhaust does not pass through the condenser but is directly led to the first evaporator through a hot gas bypass line for defrosting. The first evaporator in the defrosting zone acts as a condenser, where high-pressure, high-temperature refrigerant gas condenses and releases heat for defrosting. The refrigerant condensate then passes through a bidirectional or capillary throttling device connected between the two evaporator zones, reducing its pressure and entering the second evaporator in the undefrosted zone. There, it absorbs heat from the ambient air and evaporates. The evaporated refrigerant gas is then drawn back into the compressor, compressed, and discharged as high-temperature, high-pressure compressor exhaust, which then defrosts again. This cycle repeats multiple times until the first evaporator is defrosted. End; In the zoned hot gas defrosting circuit and its control system of the air source heat pump, the refrigerant flow direction is switched, and hot gas enters the second evaporator for defrosting, while the first evaporator undertakes the task of heat absorption; after the second evaporator defrosts, the control system closes the hot gas defrosting circuit and restores the normal heating cycle mode of the heat pump; in the air source heat pump using the zoned hot gas bypass defrosting method, the defrosting heat comes from the heat absorbed by the ambient air by the evaporator that has not been defrosted and the input work of the compressor; after the defrosting of the first evaporator of the air source water source heat pump is completed, the control system restores the normal heating cycle mode of the heat pump, and the defrosting heat comes from the heat absorbed by the water evaporator from the wastewater and the input work of the compressor.

[0006] The air source heat pump zoned hot gas bypass defrosting method and technology are characterized in that: the zoned hot gas defrosting circuit and its control system consist of two evaporators, two four-way valves, a bidirectional throttle, a hot gas check valve (hot gas passage check valve) and a bypass check valve (throttle bypass check valve, used to prevent hot gas backflow), and a hot gas inlet pipe and a throttle bypass pipe connected by pipelines; the connection method of the zoned hot gas defrosting circuit is as follows: the first port of the first four-way valve is connected to the compressor exhaust port, and the second and third ports, which can be switched to communicate with the first port respectively, are connected to the compressor exhaust port. The first port is the defrost hot gas inlet of the partitioned hot gas defrost circuit, connected to the first port (sharing a hot gas inlet port) of the second four-way valve. The connected pipeline is a hot gas inlet pipeline, and a hot gas one-way valve is installed on the pipeline. The third port is the interface for connecting the refrigerant passage inlet of the three types of heat pumps and condensers. The second and third ports of the second four-way valve, which can be switched to communicate with the first port of the second four-way valve, are respectively connected to the near ports of the refrigerant passages of the first and second evaporators. The far ports of the refrigerant passages of the two evaporators are connected by a bidirectional throttling device or a capillary throttling device. The throttling bypass is divided into two sections, the starting port of the first section is connected to the first port of the bidirectional throttling device. The first evaporator refrigerant passage's far port has a stop port connected to the second port of the first four-way valve (the same as the hot gas inlet port). A bypass check valve is installed on the front section of the pipe to prevent backflow of defrosting hot gas. The rear port is connected to the fourth port of the first four-way valve (the fourth port cannot be connected to the first port), and the terminal port is connected to the second port of the bidirectional throttling device, which is the connection port of the second evaporator refrigerant passage's far port. The fourth port of the second four-way valve (the port that cannot be connected to the first port) is reserved for the compressor return gas line connecting to the heat pump heating cycle loop. The aforementioned throttling bypass is to prevent the bidirectional throttling device from reversing when the heat pump resumes normal heating (or cooling) cycle. To mitigate the additional refrigerant flow resistance generated during operation, a throttling bypass is specially added. In defrost mode, this bypass is open because the first four-way valve is in defrost mode, and its second and fourth ports are not connected, forcing refrigerant flow between the two evaporators to pass through the bidirectional throttling device. In normal heating or cooling mode, the bypass is connected because the first four-way valve is in normal mode, and its second and fourth ports are connected, thus connecting the bypass. The bypass pipe diameter is larger than the capillary throttling device; when the bypass is connected, the refrigerant flow between the two evaporators will automatically select the bypass, resulting in low flow resistance.

[0007] The air source heat pump zoned hot gas bypass defrosting method and technology described above are characterized in that: the zoned hot gas defrosting circuit is connected to the refrigerant circulation circuit of the three types of air source heat pumps via the third port of the first four-way valve and the first and fourth ports of the second four-way valve; specifically, the third port of the first four-way valve is connected to the refrigerant passage inlet of the condenser of the single-function heating unit of the air source heat pump, or to the first port of the four-way valve (hereinafter referred to as the third four-way valve) of the refrigerant circuit of the dual-function heating and cooling unit and the triple-function heating, cooling and hot water unit of the air source heat pump; the second four-way valve... The first interface is connected to the outlet (low-pressure interface after throttling) of the heating throttling circuit, which is equipped with a throttling valve and a check valve, and is connected to the condenser of the heat pump heating cycle. When connecting to an air source heat pump dual-purpose unit (heating and cooling), it is also connected to the inlet of the cooling throttling valve in the cooling throttling circuit. The fourth interface of the second four-way valve is connected to the compressor return gas line. For air source heat pump single-purpose heating units, the return gas line is directly connected to the inlet of the gas-liquid separator. For dual-purpose heating and cooling units and triple-purpose heating, cooling, and hot water units, the return gas line is first connected to the third interface of the third four-way valve, then connected to the inlet of the gas-liquid separator via a connecting pipe, and then connected to the compressor inlet.

[0008] The air source heat pump zoned hot gas bypass defrosting method and technology described herein are characterized in that: the first and second evaporators of the zoned hot gas defrosting circuit can be evaporators of two sets of air source heat pumps A and B, respectively. These evaporators are connected in a shared manner to the heating units of two independently circulating air source heat pumps A and B, or to a dual-purpose air source heat pump unit (heating and cooling), enabling mutual defrosting and combined cooling and heating for the two sets of A and B air source heat pumps. This type of air source heat pump unit with shared defrosting for heating only, or air source heat pump unit with mutual defrosting for cooling and heating, is referred to as a mutual defrosting air source heat pump unit for heating only, or a mutual defrosting air source heat pump unit for cooling and heating, respectively, and collectively referred to as a mutual defrosting air source heat pump unit. The technology of the mutual defrosting air source heat pump unit is that the first port of the first four-way valve of the zoned hot gas defrosting circuit is only connected to the A air source heat pump unit. The compressor exhaust port of the pump is connected; its third interface is only connected to the condenser refrigeration passage inlet of the heating unit of the A air source heat pump, or the first interface of the third four-way valve of the A air source heat pump dual-purpose unit; the first interface of the second four-way valve of the partitioned hot gas defrosting circuit is connected to the heating throttling passage outlet of the heating circulation circuit of the two sets of A and B air source heat pumps, which is equipped with throttling valves and their one-way valves, or when connecting to the air source heat pump heating and cooling dual-purpose unit, it is also connected to the inlet of the refrigeration throttling valve of the refrigeration throttling passage; the fourth interface of the second four-way valve of the partitioned hot gas defrosting circuit is connected to the compressor return gas pipeline of the two sets of A and B air source heat pumps in two separate paths; during the defrosting period, only the compressor equipped with the partitioned hot gas defrosting circuit mechanism operates, and the other compressor stops operating. After defrosting, the two sets of air source heat pumps resume normal operation; the water circuits of the condensers of the two sets of A and B air source heat pumps can be connected in series or in parallel, and are equipped with hot water pumps.

[0009] The air source heat pump zoned hot gas bypass defrosting method and technology are characterized in that: the first and second evaporators of the zoned hot gas defrosting circuit can be two sets of air-source heat pump A and water-source heat pump B, with the air evaporator and water evaporator respectively. They are connected to heat pumps A and B in a shared manner by a zoned hot gas defrosting circuit and its control system of the present invention. The zoned hot gas defrosting circuit and its control system control the use of the water evaporator to absorb heat for defrosting the air evaporator. During defrosting, air source heat pump A is running, while the compressor of water source heat pump B is not running, and the hot water pump and the fan of the air evaporator are not running.

[0010] The air source heat pump zoned hot gas bypass defrosting method and technology described above are characterized in that: the mutually defrosting air source heat pump unit only requires two first and second four-way valves of a zoned hot gas defrosting circuit and its control system, in conjunction with a third four-way valve of an air source heat pump, or in conjunction with the switching control of the third and fourth four-way valves of two sets of A and B air source heat pumps. This allows for simple switching between combined heating, defrosting of the first and second evaporators, and combined cooling modes. For brevity, the following control method uses the mutually defrosting air source heat pump control method with two sets of A and B air source heat pumps as an example. For devices with only one heat pump, the control of A and B can be omitted. The specific control method is as follows:

[0011] (1) In heating mode, the first four-way valve is in the normal position, with its first and third ports connected and its second and fourth ports connected; the second four-way valve is in position A (first defrost position), with its first and second ports connected and its third and fourth ports connected; the third and fourth four-way valves of heat pumps A and B are in the heating position, with their first and second ports connected (the second port is connected to the refrigerant inlet of the condenser), and their third and fourth ports connected; compressors A and B are running, the water pumps or fans of condensers A and B are running, and the fans of evaporators A and B are running.

[0012] (2) In the first evaporator defrost mode, the first four-way valve is in the defrost position, with its first and second ports connected and its third and fourth ports connected; the second four-way valve is in position A (first defrost position), with its first and second ports connected and its third and fourth ports connected; the third four-way valve of heat pump A is in the heating position, with its first and second ports connected (the second port is connected to the refrigerant passage inlet of the condenser), and its third and fourth ports connected; heat pump B stops running; the defrost start and end commands can be selected according to the existing defrost technology; during defrost, compressor A runs and compressor B stops running; the water pumps or fans of condensers A and B stop running, the fan of evaporator B runs, and the fan of evaporator A stops running;

[0013] (3) Second evaporator defrosting mode: The first four-way valve is in the defrost position, with its first and second ports connected and its third and fourth ports connected; the second four-way valve is in position B (second defrost position), with its first and third ports connected and its second and fourth ports connected; the third four-way valve of heat pump A is in the heating position, with its first and second ports connected (the second port is connected to the refrigerant inlet of the condenser), and its third and fourth ports connected; during defrosting, compressor A runs and compressor B stops running; the water pumps or fans of condensers A and B stop running, the fan of evaporator A runs and the fan of evaporator B stops running; after defrosting, heat pumps A and B resume normal heating mode. The defrosting start and end commands can be selected according to the existing defrosting technology.

[0014] (4) Cooling mode: only for air source heat pump dual-purpose cooling and heating units and air source heat pump triple-purpose cooling, heating and hot water units. The first four-way valve is in the normal position, with its first and third ports connected and its second and fourth ports connected; the second four-way valve is in position B (second defrost position), with its first and third ports connected and its second and fourth ports connected; the third and fourth four-way valves of heat pumps A and B are in the cooling position, with their first and third ports connected and their second and fourth ports connected; heat pumps A and B run simultaneously, the water pumps or fans of condensers A and B run, and the fans of evaporators A and B run.

[0015] The aforementioned air source heat pump zoned hot gas bypass defrosting method and technology is characterized by the following: the single-unit heating unit of the mutually assisting defrosting air source heat pump, i.e., the zoned hot gas defrosting circuit and its control system, is connected to the single-unit heating unit of the air source heat pump, which is an air source heat pump water heater or an air source heat pump fan unit. It can perform three operating modes: normal heating cycle, and sequential defrosting cycle of the first and second evaporators. For the sake of brevity, only one heat pump unit is mentioned, so the "B" in A and B can be omitted. The three operating modes are:

[0016] (1) When the normal heating mode is executed, the first four-way valve is in the normal position and the second four-way valve is in position A. The refrigerant circulation process is as follows: A and B compressors, the exhaust of A compressor passes through the first four-way valve through the first and third passages, A and B condensers release heat, A and B throttling valves, A and B check valves, the second four-way valve through the first and second passages, the first evaporator, the throttling bypass front section and its bypass check valve, the first four-way valve through the second and fourth passages, the throttling bypass rear section, the second evaporator, the second four-way valve through the third and fourth passages, A and B gas-liquid separators, and A and B compressors.

[0017] (2) Execute the first evaporator defrost mode, the first four-way valve is in the defrost position, and the second four-way valve is in position A; the refrigerant circulation process is: A compressor, first four-way valve 1 and 2 passages, hot gas check valve, second four-way valve 1 and 2 passages, first evaporator defrost, bidirectional throttling device, second evaporator heat absorption, second four-way valve 3 and 4 passages, A gas-liquid separator, A compressor;

[0018] (3) Execute the second evaporator defrost mode, with the first four-way valve in the defrost position and the second four-way valve in position B; the refrigerant circulation process is as follows: A compressor, first four-way valve 1st and 2nd passages, hot gas check valve, second four-way valve 1st and 3rd passages, second evaporator defrosting, bidirectional throttling device, first evaporator heat absorption, second four-way valve 2nd and 4th passages, A gas-liquid separator, A compressor; the control mode of the shared partitioned hot gas defrost circuit and its control system, consisting of an A air source heat pump (first evaporator is a wind evaporator) and a B water source heat pump (second evaporator is a water evaporator), only adopts the above heating mode and the first evaporator defrost mode.

[0019] The air source heat pump zoned hot gas bypass defrosting method and technology described above are characterized in that: the zoned hot gas defrosting circuit and its control system are connected to the air source heat pump dual-purpose cooling and heating unit, and can perform four operating modes: normal heating and cooling cycle, and sequential defrosting cycle of the first and second evaporators; for the sake of brevity, only one heat pump unit is mentioned, so the "B" in A and B can be omitted; the four operating modes are as follows:

[0020] (1) When the normal heating mode is executed, the first four-way valve is in the normal position and the second four-way valve is in position A; the third and fourth four-way valves of heat pumps A and B are in the heating mode position; the refrigerant circulation process of heat pumps A and B is as follows: A and B compressors, refrigerant of heat pump A through the first four-way valve through the first four-way valve through the first and third passages, the third and fourth four-way valves of heat pumps A and B through the first and second passages, A and B condensers release heat, A and B heating throttling valves, A and B check valves, the second four-way valve through the first and second passages, the first evaporator absorbs heat, the bypass check valve (throttling bypass front section), the first four-way valve through the second and fourth passages, the throttling bypass rear section, the second evaporator absorbs heat, the second four-way valve through the third and fourth passages, the third and fourth four-way valves of heat pumps A and B through the third and fourth passages, A and B gas-liquid separators, A and B compressors;

[0021] (2) When the normal cooling mode is executed, the first four-way valve is in the normal position, the second four-way valve is in position B (the second evaporator defrost position), and the third and fourth four-way valves of heat pumps A and B are in the cooling position; the refrigerant circulation process of heat pumps A and B is as follows: A and B compressors, the refrigerant of heat pump A passes through the first four-way valve through the first four-way valve through the first and third passages, the third and fourth four-way valves of heat pumps A and B through the first and third passages, the second four-way valve through the fourth and second passages, the first evaporator, which acts as a condenser to release heat, the bypass check valve (the first section of the throttling bypass), the first four-way valve through the second and fourth passages, the second evaporator, which acts as a condenser to release heat, the second four-way valve through the third and first passages, the A and B cooling throttling valves, the A and B cooling check valves, the A and B condensers, which act as evaporators to absorb heat and produce chilled water, the third and fourth four-way valves of heat pumps through the second and fourth passages, the A and B gas-liquid separators, and the A and B compressors;

[0022] (3) When the first evaporator defrost mode is executed, the first four-way valve is in the defrost position, the second four-way valve is in position A, and the third four-way valve is in the normal position; the refrigerant circulation process is as follows: A compressor, first four-way valve 1 and 2 passages, hot gas check valve, second four-way valve 1 and 2 passages, first evaporator defrost, bidirectional throttling device, second evaporator heat absorption, second four-way valve 3 and 4 passages, A third four-way valve 3 and 4 passages, A gas-liquid separator, A compressor;

[0023] (4) When the second evaporator defrost mode is executed, the first four-way valve is in the defrost mode position, the second four-way valve is in position B, and the third four-way valve is in the normal position; the refrigerant circulation process is as follows: A compressor, first four-way valve 1 and 2 passages, hot gas check valve, second four-way valve 1 and 3 passages, second evaporator defrost, bidirectional throttling device, first evaporator heat absorption, second four-way valve 2 and 4 passages, A third four-way valve 3 and 4 passages, A gas-liquid separator, A compressor.

[0024] The air source heat pump zoned hot gas bypass defrosting method and technology are characterized in that: when the first and second evaporators of the air source heat pump are arranged vertically, the first evaporator, which defrosts first, is arranged on top, and the second evaporator, which defrosts later, is arranged on the bottom; the evaporators arranged side by side with top air blowing are designated as the first evaporator, with the evaporator that houses the main components of the zoned hot gas defrosting circuit installed; the air source water source heat pump water heater connected to the zoned hot gas defrosting circuit and its control system has its air evaporator installed independently outdoors, while the water evaporator, condenser, compressor, and control system are all installed indoors.

[0025] The main innovations of this invention are as follows: 1. This invention proposes an innovative defrosting method, namely "an air-source heat pump zoned hot gas bypass defrosting method and its technology." The defrosting principle is as follows: the air-source heat pump defrosts in zones, with the evaporators of the finned coil air heat exchanger being defrosted sequentially in two zones, the first and second evaporators. During defrosting, the first evaporator acts as a condenser; the refrigerant liquid condensed during defrosting is throttled into the second evaporator through a bidirectional throttling device between the two evaporators. In the second evaporator, it absorbs heat from the ambient air and evaporates. The evaporated refrigerant is then drawn into the compressor and compressed into high-pressure, high-temperature hot gas for defrosting. Most of the heat used for defrosting comes from absorbing heat from the ambient air, with a small portion being the compressor's input power. This invention overcomes the problem of existing defrosting methods lacking a cheap heat source. Under the same heat consumption during defrosting, this invention can save more than 70% of electrical energy. Secondly, because this invention... The refrigerant evaporation in the indirect evaporator has a heat source, resulting in high compressor intake pressure, large intake volume, high compressor input power, and higher discharge pressure and temperature. The high-pressure, high-temperature refrigerant carries more heat, thus accelerating defrosting and further improving equipment operating efficiency and heat output capacity, while shortening the total defrosting time. Furthermore, compared to reverse cycle defrosting, it does not require changing the refrigerant circulation direction, reducing downtime and reversal cycles, and minimizing the time and energy consumption required to rebuild stable equipment operation. It also avoids impacting the equipment and prevents "oil run-through," allowing the equipment to operate stably immediately after defrosting. This further reduces the defrosting time percentage and relatively increases equipment output, demonstrating significant advantages. This invention overcomes almost all the shortcomings of existing defrosting methods and solves the problem of lacking a cheap energy source for defrosting air source heat pumps in winter, representing a groundbreaking innovation in air source heat pump defrosting methods.

[0026] 2. The present invention provides a zoned hot gas bypass defrosting method and technology for air source heat pumps. Technically, it constructs a universal "zoned hot gas defrosting circuit." Its main components only require the addition of two four-way valves, a capillary tube bidirectional throttling device, and two one-way valves, resulting in a low-cost "zoned hot gas defrosting circuit." The two evaporators in the designed "zoned hot gas defrosting circuit" can be combined with the finned coil heat exchanger of the original air source heat pump. The zoned hot gas defrosting circuit and its control system are universal, capable of connecting to air source heat pump water heaters or air source heat pump hot air blowers for single-function heating, central air conditioning water chillers or ordinary household air conditioning units for dual-function heating and cooling systems, or air source heat pump three-function systems for heating, cooling, and hot water, demonstrating strong versatility.

[0027] 3. The present invention provides a zoned hot gas bypass defrosting method and technology for air source heat pumps. Using one zoned hot gas defrosting circuit and its control system, two sets of air source heat pumps can be created to mutually defrost and jointly heat or cool. This device can be uniformly named "mutual defrosting air source heat pump". The method of connecting the second set of air source heat pumps is simple, and only one zoned hot gas defrosting circuit and its control system are used to control all operating modes of the two heat pumps.

[0028] 4. The present invention relates to a zoned hot gas bypass defrosting method and technology for air source heat pumps. In the refrigerant circulation loop of a mutually defrosting air source heat pump, an innovative "three-nested dual-path switching technology" is used. The first four-way valve is used to switch between defrosting and normal heating / cooling modes; the second four-way valve is used to switch between the first and second evaporators in defrosting mode; and the third and fourth four-way valves of the heat pump are used in conjunction with the switching to complete the switching of the heat pump's heating / cooling modes. The design is ingenious and the control is simple.

[0029] 5. This invention features a specially designed bidirectional throttling bypass, utilizing the 2nd and 4th ports of the first four-way valve as the on / off switch for connecting and disconnecting the throttling bypass. Furthermore, it is linked to defrosting and resuming normal operation. This cleverly ensures that during defrosting, the refrigerant can only pass through the bidirectional throttling bypass between the two evaporators, thus guaranteeing the establishment of a pressure difference between the two evaporators. This allows one evaporator to function as a condenser for defrosting, while the other functions as an evaporator for heat absorption. During normal heating or cooling cycles, the connection of the throttling bypass and the refrigerant flow in heating or cooling cycles both bypass the bidirectional throttling bypass, instead flowing through a throttling system with a larger pipe diameter and lower resistance. The bypass, entering two evaporators (which act as condensers during the refrigeration cycle), reduces refrigerant flow resistance losses and perfectly achieves the connection between defrosting and normal heating / refrigeration cycles. Although, theoretically, the throttling bypass can be replaced by installing a bypass solenoid valve for the main pipe bypass, in large heat pump systems, large-diameter solenoid valves are hard to find, and even if they are available, they are expensive and unreliable. However, the first four-way valve used in this invention completes the switching control of the defrosting mode and normal mode, as well as the connection and disconnection of the throttling bypass, simplifying the control system, saving manufacturing costs, and increasing reliability compared to the bypass controlled by the solenoid valve.

[0030] In summary, the air source heat pump zoned hot air bypass defrosting method and its technology of the present invention have significant innovations in terms of method and technology; the technical design of the present invention can be described as extremely advanced, extremely simple, and extremely easy to control, and it has ushered in a new era of "mutual defrosting air source heat pump" in which two sets of air source heat pumps mutually assist defrosting and jointly heat or cool; no relevant reports of the above design were found in the literature and patent search.

[0031] The technology of this invention can directly save the high-grade electrical energy consumed in defrosting air source heat pumps, shorten defrosting time, and improve the heating capacity of heat pumps in winter, providing technical support for the normal operation of air source heat pumps in winter. More broadly, the technology of this invention solves the winter concerns for the widespread use of energy-saving air source heat pump products. Mutual-assisted defrosting air source heat pump water heaters can largely replace electric water heaters for hot water production and for heating, resulting in significant cumulative energy savings. This also highlights the significant technical importance of this invention's zoned hot air bypass defrosting method for air source heat pumps. This invention is innovative, advanced, and practical, and should be granted a patent as soon as possible. Attached Figure Description

[0032] Figure 1 This is an embodiment 1 of the air source heat pump zoned hot air bypass defrosting method and technology of the present invention. It is a structural schematic diagram and working principle explanation diagram of a mutual defrosting air source heat pump unit that is connected to a heat pump used only for heating, and operates in the first evaporator defrosting mode.

[0033] Figure 2This is a flowchart illustrating the normal heating mode of an air source heat pump zoned hot air bypass defrosting method and technology according to Embodiment 1 of the present invention.

[0034] Figure 3 This is Embodiment 2 of the present invention, which describes a zoned hot air bypass defrosting method and technology for an air source heat pump. It is a structural schematic diagram and a diagram illustrating the mutual defrosting principle of a mutually defrosting air source heat pump that connects to two sets of heat pumps used only for heating, and operates in the defrosting mode of the first evaporator.

[0035] Figure 4 This is Embodiment 3 of the present invention, which describes a zoned hot air bypass defrosting method and technology for an air source heat pump. It is a structural schematic diagram and working principle diagram of a mutually defrosting air source heat pump that is connected to a set of dual-purpose (heating and cooling) heat pumps, and operates in the first evaporator defrosting mode.

[0036] Figure 5 This is Embodiment 3 of the present invention, which describes the normal heating mode of an air source heat pump with zoned hot air bypass defrosting method and technology.

[0037] Figure 6 This is Embodiment 4 of the present invention, which describes a zoned hot air bypass defrosting method and technology for an air source heat pump. It is a structural schematic diagram and working principle diagram of a mutually defrosting air source heat pump that connects to two sets of dual-purpose (heating and cooling) heat pumps, and operates in the first evaporator defrosting mode.

[0038] Figure 7 This is Embodiment 4 of the present invention, which describes a zoned hot air bypass defrosting method and technology for an air source heat pump, operating in normal heating mode.

[0039] Figure 8 This is Embodiment 4 of the present invention, which describes a zoned hot gas bypass defrosting method and technology for an air source heat pump, operating in normal cooling mode.

[0040] Figure 9 This is Embodiment 5 of the present invention, which describes a zoned hot air bypass defrosting method and technology for an air source heat pump. It is a schematic diagram of the structure and working principle of a set of air source and water source heat pump water heaters, and is running in the first defrosting mode.

[0041] Figure 10 This is Embodiment 6 of the present invention, which describes a partitioned hot air bypass defrosting method and technology for an air source heat pump. It is a schematic diagram and working principle diagram of a system that connects an air source heat pump water heater and a water source heat pump water heater, and operates in the first defrosting mode. Detailed Implementation

[0042] The present invention will be further described below with reference to the embodiments and accompanying drawings, but the present invention is not limited thereto.

[0043] Example 1

[0044] This invention discloses a zoned hot air bypass defrosting method and technology for air source heat pumps, including its working principle and the structure of a mutually defrosting air source heat pump that connects to a single-use heating heat pump. Figure 1 , 2 To explain, Figure 1 Run the first evaporator defrost mode. Figure 2 Operating in normal heating mode; see Figure 1This invention discloses a zoned hot gas bypass defrosting method and technology for an air source heat pump. The zoned hot gas defrosting circuit and its control system consist of two evaporators H1 and H2 in the zone, two four-way valves S1 and S2, a bidirectional throttle J2, a hot gas one-way valve D2 (hot gas passage one-way valve), and a bypass one-way valve D3 (throttle bypass one-way valve, used to start and stop reverse hot gas flow), and a hot gas inlet pipe L1 connected by pipelines, and a throttle bypass pipe (L4+L5). The connection method of the zoned hot gas defrosting circuit is as follows: the first port ① of the first four-way valve S1 is connected to the compressor exhaust port, and the second and third ports ② and ③ can be connected to the first... The interface switches between two interconnected interfaces. Interface ② (2nd interface) is the defrost hot gas inlet of the partitioned hot gas defrost circuit, connected to interface ① (shared hot gas inlet) of the second four-way valve S2. The connected pipeline is the hot gas inlet pipeline L1, on which a hot gas one-way valve D2 is installed. Interface ③ (3rd interface) is the interface connecting the heat pump and the refrigerant passage inlet of the condenser H3. Interfaces ② and ③ of the second four-way valve S2, which can be switched to interface ① (1st interface) of the second four-way valve S2, are respectively connected to the near ports of the refrigerant passages of the first and second evaporators H1 and H2. The far ports of the refrigerant passages of the two evaporators are connected using a bidirectional throttling device or a capillary throttling device J2. The throttling bypass is... The two sections, L4 and L5, have the following connections: the starting port of the front section is connected to the first port of the bidirectional throttle J2, which is the far port of the refrigerant passage of the first evaporator H1, and the stopping port is connected to the second interface ② of the first four-way valve S1 (the same as the hot gas inlet interface). A bypass check valve D3 is installed on the front section to prevent the defrosting hot gas flow from flowing backward. The starting port of the rear section L5 is connected to the fourth interface ④ of the first four-way valve S1 (the fourth interface cannot be connected to the first interface), and the ending port is connected to the second port of the bidirectional throttle J2, which is the connection port of the far port of the refrigerant passage of the second evaporator. The fourth interface ④ of the second four-way valve S2 (the interface that cannot be connected to the first interface) is reserved for the compressor return gas of the heat pump heating cycle loop. Pipeline L3; the aforementioned throttling bypass (L4+L5) is a specially added throttling bypass to avoid the additional refrigerant flow resistance generated by the bidirectional throttling device J2 when the heat pump resumes normal heating (or cooling) cycle; the aforementioned throttling bypass is in a disconnected state in defrost mode because the first four-way valve S1 is in the defrost mode position, and the second and fourth ports ② and ④ of the first four-way valve S1 are not connected, so the refrigerant flow between the two evaporators H1 and H2 must pass through the bidirectional throttling device J2; the aforementioned throttling bypass is in a connected state in normal heating or cooling mode because the first four-way valve S1 is in the normal mode position, and the second and fourth ports ② and ④ of the first four-way valve S1 are connected, so the throttling bypass is connected;The diameter of the throttling bypass (L4+L5) is larger than that of the capillary throttling device. When the throttling bypass (L4+L5) is connected, the refrigerant flow between the two evaporators will automatically select the throttling bypass, resulting in low flow resistance.

[0045] The partitioned hot gas defrosting circuit is connected to the refrigerant circulation circuit of the air source heat pump via the 3rd port ③ of the first four-way valve S1 and the 1st and 4th ports ① and ④ of the second four-way valve S2. The connection method in Embodiment 1 is as follows: the 3rd port ③ of the first four-way valve S1 is connected to the refrigerant passage inlet of the condenser H3 of the air source heat pump's heating unit; the 1st port of the second four-way valve S2 is connected to the outlet (low-pressure port after throttling) of the heating throttling passage of the condenser H3 of the heat pump heating cycle, which is equipped with a throttling valve J1 and a one-way valve D1; the 4th port ④ is connected to the return gas pipeline L3 of the compressor Y1, and then the return gas pipeline L3 is connected to the inlet of the gas-liquid separator G.

[0046] The aforementioned zoned hot gas defrosting circuit and its control system can easily achieve heat pump heating and first and second defrosting cycles by simply controlling the switching of three four-way valves S1, S2, and S3 (first, second, and third positions). Its control method and refrigerant flow are as follows:

[0047] (1) Heating mode (hot water production), see appendix Figure 2 The first four-way valve S1 is in the normal position, with its first and third ports ① and ③ connected, and its second and fourth ports ② and ④ connected; the second four-way valve S2 is in position A (first defrost position), with its first and second ports ① and ② connected, and its third and fourth ports ③ and ④ connected; the refrigerant circulation process is as follows: compressor Y1, the first four-way valve S1 ports ① and ③ are connected, condenser H3 releases heat, throttle valve J1, check valve D1, the second four-way valve S2 ports ① and ② are connected, the first evaporator H1 absorbs heat, enters the throttle bypass front section L4 and its bypass check valve D3, the first four-way valve S1 ports ② and ④, the throttle bypass rear section L5, the second evaporator H2 absorbs heat, the second four-way valve S2 ports ③ and ④, gas-liquid separator G, compressor Y1;

[0048] (2) First evaporator defrosting mode, see appendix Figure 1 The first four-way valve S1 is in the defrost position; the second four-way valve is in position A (first defrost position); the refrigerant circulation process is as follows: compressor Y1, first four-way valve ① and ② passages, hot gas check valve D2, second four-way valve S2 ① and ② passages, first evaporator H1 defrosts, bidirectional throttle J2, second evaporator H2 absorbs heat, second four-way valve S2 ③ and ④ passages, gas-liquid separator G, compressor Y1;

[0049] (3) Second evaporator defrost mode, first four-way valve S1 is in the defrost position; Figure 1The second four-way valve S2 is switched to position B (second defrost position), with its first and third ports ① and ③ connected, and its second and fourth ports ② and ④ connected. The refrigerant circulation process is as follows: compressor Y1, first four-way valve ① and ② passages, hot gas check valve D2, second four-way valve S2 ① and ③ passages, second evaporator H2 defrosting, bidirectional throttling device J2, first evaporator H1 absorbing heat, second four-way valve S2 ② and ④ passages, gas-liquid separator G, compressor Y1. After defrosting, normal heating mode is restored. The defrosting start and end commands can be selected according to the existing defrosting technology.

[0050] When the first and second evaporators of the air source heat pump are arranged vertically, the first evaporator, which defrosts first, is arranged on top, and the second evaporator, which defrosts later, is arranged on the bottom. For the top-blown evaporators arranged side by side, the evaporator that houses the main components of the zoned hot gas defrosting circuit is the first evaporator.

[0051] Example 2 Figure 3 This is Embodiment 2 of the present invention, which describes a zoned hot air bypass defrosting method and technology for an air source heat pump. It is a schematic diagram of the structure and a diagram illustrating the mutual defrosting principle of an air source heat pump that connects to two single-use heating heat pumps, operating in the first evaporator defrosting mode. Embodiment 2 Figure 3 Compared with Example 1 Figure 1 The difference lies in the addition of a second air source heat pump water heater, consisting of compressor Y2, condenser H4, throttle valve J3, and fourth one-way valve D4, connected sequentially by pipes. The outlet of the fourth one-way valve D4 is connected to the first port ① of the second four-way valve S2, and the inlet of the gas-liquid separator G2 is connected to the fourth port ④ of the second four-way valve S2. Thus, based on embodiment 1, a partitioned hot gas defrosting circuit and its control system are constructed, connecting to a dual-heat pump mutual defrosting air source heat pump water heater that is a single-use heating heat pump connected to two air source heat pumps. When the dual-heat pump mutual defrosting air source heat pump water heater executes the first and second evaporator defrosting modes, except that compressor Y2 stops running, all other operations are the same as in embodiment 1, and the refrigerant only runs in the first heat pump system. After defrosting, compressor Y2 resumes operation, and the two evaporators jointly serve the two heat pumps. The first and second evaporators are the original evaporators of the two heat pumps.

[0052] Example 3

[0053] Embodiment 4 of the present invention provides a zoned hot air bypass defrosting method and technology for air source heat pumps. This embodiment describes the zoned hot air defrosting circuit and its control system, and the structure and working principle of a mutually defrosting air source heat pump connected to a dual-purpose (heating and cooling) heat pump. (The remaining text appears to be a fragmented and incomplete description of the invention.) Figure 4 , 5 illustrate, Figure 4 Run the first evaporator defrost mode. Figure 5 Running in normal heating mode;

[0054] The similarities between Example 3 and Example 1 are: the structure and control method of the partitioned hot air defrosting circuit and its control system are exactly the same, so they will not be described again; the difference is that Example 3 is connected to an air source heat pump dual-purpose unit for heating and cooling, which is a central air conditioning chiller / hot water unit for both heating and cooling. Its condenser is a water heat exchanger, which outputs hot water for heating in winter and chilled water for cooling in summer; or a commonly used household chiller / heater water unit, which outputs air heat exchanger, which outputs hot air for heating in winter and chilled air for cooling in summer; the evaporators mentioned in this invention are all finned coil air conditioners installed outdoors. The evaporator in the partitioned defrosting method of this invention, namely the outdoor finned coil fan used by a heat pump, is made into two partitions, which are referred to as the first and second evaporators for convenience. For household air conditioning water heaters, because of their relatively low power, it is recommended that the first and second evaporators be arranged vertically, with the first evaporator (defrosting first) placed on top and the second evaporator (defrosting later) placed on the bottom, each equipped with a fan. For central air conditioning water heaters, which commonly use a top-blowing method, it is recommended that the evaporators be arranged side-by-side, with the evaporator connected to the starting interface of the throttle bypass being designated as the first evaporator.

[0055] Example 3 Figure 4 , 5 Compared with Example 1 Figure 1 , 2 Compared to the previous version, the air-source heat pump dual-purpose unit with partitioned hot air defrosting circuit has an additional four-way valve (denoted as the third four-way valve S3). The third port ③ of the first four-way valve S1 in the partitioned hot air defrosting circuit is connected to the first port ① of the third four-way valve S3; the second port ② of the third four-way valve S3 is connected to the refrigerant passage interface of the condenser H3; the third port ③ of the third four-way valve S3 is connected to the fourth port ④ of the second four-way valve S2; the fourth port ④ of the third four-way valve S3 is connected to the inlet of the gas-liquid separator G in the compressor Y1 intake pipe; the first port of the second four-way valve S2 is connected to the outlet end of the condenser H3 (the outlet end during the heating process), and a refrigeration passage with a refrigeration check valve J3 is added. Other structures are the same as before. Figure 1 The same applies, and will not be explained further.

[0056] Example 3 describes a dual-purpose air-source heat pump with a zoned hot gas defrosting circuit and its control system, which can perform four operating modes: normal heating, cooling, first defrosting, and second defrosting. Its control method and refrigeration process are as follows:

[0057] (1) First (evaporator) defrosting mode, see appendix Figure 4The first four-way valve S1 is in the defrost position, the second four-way valve S2 is in position A, and the third four-way valve S3 is in the normal heating position. Its first and third ports ① and ② are connected, and its second and fourth ports ③ and ④ are connected. The refrigerant circulation process is as follows: compressor Y1, the first four-way valve ports ① and ② are connected, hot gas passage L1 and its hot gas check valve D2, the second four-way valve S2 ports ① and ② are connected, the first evaporator H1 (defrost), the bidirectional throttle J2, the second evaporator H2 (heat absorption), the second four-way valve S2 ports ③ and ④ are connected, the third four-way valve ports ③ and ④ are connected, the gas-liquid separator G, and the compressor Y1. The compressor Y1 and the fan F2 of the second evaporator are running, while the water pump of the condenser and the fan F1 of the first evaporator are not running.

[0058] (2) Normal heating mode (hot water production), see appendix. Figure 5 The first four-way valve S1 is in the normal position, the second four-way valve S2 is in position A, and the third four-way valve S3 is in the normal heating position. The refrigerant circulation process is as follows: compressor Y1, the first four-way valve S1 through ports ① and ③, the third four-way valve S3 through ports ① and ②, condenser H3 releases heat, throttle valve J1, check valve D1, the second four-way valve S2 through ports ① and ②, the first evaporator H1 absorbs heat, the throttle bypass front section L5 and its bypass check valve D3, the first four-way valve S1 through ports ② and ④, the throttle bypass rear section L6, the second evaporator H2 absorbs heat, the second four-way valve S2 through ports ③ and ④, the third four-way valve through ports ③ and ④, gas-liquid separator G, compressor Y1; the fan F2 of compressor Y1 and the first and second evaporators is running, and the water pump of the condenser is running;

[0059] (3) Cooling mode, Figure 5 The switching of the second and third four-way valves: the first four-way valve S1 remains in the normal position; the second four-way valve S2 is in position B (second defrost position) at interface ① and ③; and the third four-way valve S3 is in the cooling position at interface ① and ③. Its refrigerant flow is the same as... Figure 5 The heating cycle shown is the reverse flow: Compressor Y1, first four-way valve S1, interfaces ① and ③, third four-way valve, interfaces ① and ③, second four-way valve, interface ④ and ②, first evaporator H1 releases heat, bypass of the first section L5 of the throttling bypass and its bypass check valve D3, first four-way valve S1, interfaces ② and ④, throttling bypass of the second section L6, second evaporator H2 releases heat, second four-way valve S2, interfaces ③ and ①, throttling valve J3, cooling check valve D4, condenser H3 (cooling process is evaporator, cooling water or cold air), third four-way valve, interface ② and ④, gas-liquid separator G, compressor Y1; compressor Y1, fan F2 of the first and second evaporators are running, and the water pump of the condenser is running;

[0060] (4) Second (evaporator) defrosting mode, Figure 4The second four-way valve S2 can be switched to the ①③ interface passage; the refrigerant circulation process in defrost mode is as follows: compressor Y1, first four-way valve ①② interface passage, hot gas check valve D2, second four-way valve S2 ①③ passage, second evaporator S2 defrosts, bidirectional throttle J2, first evaporator H1 absorbs heat, second four-way valve S2 ②④ passage, third four-way valve ③④ interface passage, gas-liquid separator G, compressor Y1.

[0061] Example 4

[0062] Example 4: A zoned hot air bypass defrosting method and technology for an air source heat pump according to the present invention, a mutually defrosting air source heat pump that connects to two sets of dual-purpose (heating and cooling) heat pumps, illustrated in the following diagram: Figure 6 , 7 8. Explanation Figure 6 , 7 8 and 8 represent the second defrost mode, normal heating mode, and cooling mode of Example 4, respectively.

[0063] like Figure 7 In Embodiment 4, the partitioned hot air defrosting circuit and its control system are connected in a shared manner to two air source heat pump dual-purpose units, which can be called a dual-heat pump dual-purpose unit with mutual defrosting. The difference between Embodiment 4 and Embodiment 3 is only that the partitioned hot air defrosting circuit and its control system are connected to an additional air source heat pump dual-purpose unit. The new heat pump is designated as Heat Pump A, and the original heat pump is designated as Heat Pump B. Heat Pumps A and B have the same power and structure. The shared manner is that the partitioned hot air defrosting circuit is installed on Heat Pump A system, and its connection method with Heat Pump A is the same as in Embodiment 3. Figure 4 The same applies and will not be described again; the difference between Example 4 and Example 3 is that: the fourth port ④ of the second four-way valve S2 of the partitioned hot gas defrosting circuit is connected in parallel with the third port ③ of the third and fourth four-way valves S3 and S4 of sets A and B; the first port of the second four-way valve is connected to the outlet of the throttling valves J1 and J4 and their one-way valves D1 and D5 of the heating cycle of the two heat pumps A and B, and is also connected to the inlet of the throttling valves J2 and J5 of the refrigeration cycle of the two heat pumps A and B;

[0064] The aforementioned dual-heat pump air-source heat pump dual-use unit with mutual defrosting capability allows two air-source heat pumps, A and B, to jointly execute normal heating and cooling cycles. It also features four different operating modes: one for the first evaporator and one for the second, with the first and second evaporators defrosting sequentially. In the defrosting mode, only heat pump A operates, while heat pump B is stopped. The refrigerant flow and control methods for the four operating modes are as follows:

[0065] (1) When executing the first (evaporator) defrost mode, see Figure 4The first four-way valve S1 is in the defrost position, the second four-way valve S2 is in position A, and the third four-way valve S3 is in the normal position. Compressor A is running, and compressor B is stopped. The refrigerant circulation process is as follows: compressor A Y1, first four-way valve S1 ①② interface passage, hot gas check valve D2, second four-way valve S2 ①② interface passage, first evaporator H1 defrost, bidirectional throttling device J2, second evaporator H2 absorb heat, second four-way valve S2 ③④ interface passage, third four-way valve S3 ③④ passage, A gas-liquid separator G1, compressor A Y1; heat pump B stops running, fan F2 of the second evaporator runs, and fan F1 of the first evaporator stops running.

[0066] (2) When executing the second (evaporator) defrost mode, see Figure 6 The first four-way valve S1 is in defrost mode, the second four-way valve S2 is in position B, and the third four-way valve S3 is in normal position; the refrigerant circulation process is as follows: A. Compressor Y1, first four-way valve ①② interface passage, hot gas check valve D2, second four-way valve S2 ①③ interface passage, second evaporator H2 defrost, bidirectional throttle J2, first evaporator H1 absorb heat, second four-way valve S2 ②④ interface passage, third four-way valve S3 ③④ interface passage, gas-liquid separator G1, compressor Y1; B. Heat pump stops running;

[0067] (3) When performing a normal heating cycle, see Figure 7 The first four-way valve S1 is in the normal position, and the second four-way valve S2 is in position A; the third and fourth four-way valves S3 and S4 are in the heating mode position (paths ① and ②); the two compressors Y1 and Y2 are running, and the refrigerant of the two heat pumps is circulating; the refrigerant circulation process of heat pumps A and B is as follows: compressors A and B (Y1 and Y2), the first four-way valve S1 of heat pump A (paths ① and ③), the third and fourth four-way valves S3 and S4 of heat pumps A and B (paths ① and ②), and condensers H3 and H4 of heat pumps A and B (heat release). A and B (heating) throttling valves J1 and J4, A and B one-way valves D1 and D5, second four-way valve S2 (①② passage), A first evaporator H1 (heat absorption), throttling bypass front section L5 and its bypass one-way valve D3, first four-way valve S1 (②④ passage), throttling bypass rear section L6, second evaporator H2 (heat absorption), second four-way valve S2 (③④ passage), A and B heat pump third and fourth four-way valves S3 and S4 (③④ passage), A and B gas-liquid separators G1 and G2, A and B compressors Y1 and Y2;

[0068] (4) When executing normal cooling mode, see [link / reference] Figure 8The first four-way valve S1 is in the normal position, the second four-way valve S2 is in position B, and the third and fourth four-way valves S3 and S4 of heat pumps A and B are in the cooling position. The refrigerant circulation paths of heat pumps A and B are as follows: compressors Y1 and Y2 of A and B, the first four-way valve S1 of heat pump A (paths ① and ③), the third and fourth four-way valves of heat pumps A and B (paths ① and ③), the second four-way valve S2 (paths ④ and ②), the first evaporator H1 (acting as a condenser for heat release), the throttling bypass front section L5 and its bypass check valve D3, and the first four-way valve S1 (paths ② and ④). The following components are included: L6 (after the throttling bypass), H2 (as a condenser for heat release), a second four-way valve (③① passage), J3 and J5 (refrigeration throttling valves for A and B), D2 and D6 (refrigeration one-way valves for A and B), H3 and H4 (condensers for A and B, used as evaporators for heat absorption and chilled water production), S3 and S4 (two and four four-way valves for A and B heat pumps, passages 2 and 4), G1 and G2 (gas-liquid separators for A and B), and Y1 and Y2 (compressors for A and B). In Embodiment 4 of this invention, the condensers of the two air source heat pumps can be replaced with air heat exchangers, and the heat pumps output hot or cold air.

[0069] Example 5

[0070] Figure 9 This is Embodiment 5 of the present invention, which describes a zoned hot air bypass defrosting method and technology for an air-source heat pump. It is a schematic diagram and working principle illustration of a system connected to an air-source / water-source heat pump water heater, operating in the first defrosting mode. Embodiment 5 of the present invention... Figure 1 The difference between Example 1 and Example 5 is that the second evaporator is replaced by a water evaporator H2 that uses bath wastewater or geothermal water as a heat source, and is equipped with a wastewater pump P2. The control of the heating mode and the first evaporator defrosting mode is the same as in Example 1. However, when heating water, the refrigerant passes through the first evaporator (air evaporator) H1 and the second water evaporator in sequence. When both the wastewater pump P2 and the fan F1 are running, the heat pump absorbs heat from both the ambient air and the wastewater. Since the combined evaporation area of ​​the two evaporators is increased, the heating capacity is also greater. When there is no wastewater, the wastewater pump stops, and only the air evaporator absorbs heat. If the ambient temperature is below 0°C, the fan is generally not turned on, and the wastewater source provides the heat for refrigerant evaporation. The heat pump in Example 5 does not perform a second defrosting mode. After the first evaporator defrosts, it returns to the normal heating mode.

[0071] Example 6 Figure 10 This is Embodiment 6 of the present invention, which describes a zoned hot air bypass defrosting method and technology for air source heat pumps. It is a schematic diagram and working principle illustration of a system connecting an air source heat pump water heater and a water source heat pump water heater, operating in the first defrosting mode. Embodiment 5 of the present invention... Figure 3The difference in Example 2 is that heat pump B is a water source heat pump, and the second evaporator is a water evaporator, using bath wastewater or geothermal water as the heat source. The control of the heating mode and the first evaporator defrosting mode is the same as in Example 3. However, when heating water, the compressors of both heat pumps A and B are running. The refrigerant passes through the first evaporator H1 and the second water evaporator in sequence. When both wastewater pump P2 and fan F1 are running, the heat pump absorbs heat from both the ambient air and the wastewater. Since the combined area of ​​the two evaporators is increased, the heating capacity is also greater. If there is no wastewater, either the compressor of heat pump A or B can be turned on, the wastewater pump stops, the fan runs, and the air evaporator absorbs heat. If the ambient temperature is below 0°C, the fan is generally not turned on, and the wastewater source provides the heat for refrigerant evaporation. Either the compressor of heat pump A or B can be turned on. In Example 5, the heat pump does not perform the second defrosting mode. After the first evaporator defrosts, it returns to the normal heating mode.

Claims

1. A zoned hot gas bypass defrosting method for an air source heat pump, wherein the air source heat pump comprises: Air source heat pumps: single-function heating unit, dual-function cooling and heating unit, and triple-function cooling, heating, and hot water unit. The refrigerant circulation loops of the above three types of air source heat pumps all include the following basic components: compressor, condenser, expansion valve, evaporator, gas-liquid separator, and check valve. The condenser is equipped with a water pump or fan, and the evaporator is a finned coil air heat exchanger equipped with a fan. Air source heat pumps that can be used for both cooling and heating also include a four-way valve; air source heat pumps that can be used for both cooling, heating, and hot water also include a four-way valve, a three-way valve, and a domestic hot water heat exchanger. The characteristic feature is that the air source heat pump zoned hot gas bypass defrosting method involves modifying and adding a zoned hot gas defrosting loop and its control system to the refrigerant circulation loops of the above three types of air source heat pumps. The principle of the zoned hot gas bypass defrosting method is as follows: the evaporator of the air source heat pump is divided into two zones, referred to as the first and second evaporators, respectively. Defrosting is performed sequentially by bypassing hot gas, i.e., the first and second evaporators are defrosted sequentially. During defrosting, the compressor exhaust does not pass through the condenser; all hot gas passes directly through the bypass. The refrigerant gas is defrosted by a pipeline to the first evaporator. The first evaporator in the defrosting zone acts as a condenser, where high-pressure, high-temperature refrigerant gas condenses and releases heat for defrosting. The condensed refrigerant then passes through a bidirectional or capillary throttling device connected between the two evaporators, reducing its pressure and allowing it to enter the second evaporator in the undefrosted zone. There, it absorbs heat from the ambient air and evaporates. The evaporated refrigerant gas is then drawn into the compressor, compressed, and discharged as high-temperature, high-pressure gas, which then defrosts again. This cycle repeats multiple times until the first evaporator is defrosted. The partitioned hot gas defrosting circuit and its control system switch the refrigerant flow direction, allowing hot gas to enter the second evaporator for defrosting, while the first evaporator absorbs heat. Once the second evaporator is defrosted, the control system shuts down the hot gas defrosting circuit, restoring the heat pump to its normal heating cycle mode. In a heat pump using partitioned hot gas bypass defrosting, the heat for defrosting comes from the heat absorbed from the ambient air by the undefrosted evaporator and the input power of the compressor. The partitioned hot gas defrosting circuit and its control system consist of two evaporators, two four-way valves, a bidirectional throttle, a hot gas check valve and a bypass check valve, and a hot gas inlet pipe and a throttle bypass connected by pipelines. The partitioned hot gas defrosting circuit is connected as follows: the first port of the first four-way valve is connected to the compressor exhaust port; the second and third ports, which can be switched to communicate with the first port respectively, serve as the defrosting hot gas inlet for the partitioned hot gas defrosting circuit and are connected to the first port of the second four-way valve. The connected pipeline is a hot gas inlet pipeline, and a hot gas one-way valve is installed on the pipeline; the third interface is the interface for connecting the refrigerant passage inlet of the three types of air source heat pumps and condensers; the second and third interfaces of the second four-way valve, that is, the two interfaces that can be switched to communicate with the first interface of the second four-way valve respectively, are connected to the near ports of the refrigerant passages of the first and second evaporators respectively, and the far ports of the refrigerant passages of the two evaporators are connected by a bidirectional throttling device or a capillary throttling device; the throttling bypass is divided into two sections, the starting port of the front section is connected to the first port of the bidirectional throttling device, that is, the refrigerant passage of the first evaporator. The far end of the passage is connected to the second port of the first four-way valve. A bypass check valve is installed on the front section of the pipeline to prevent backflow of defrosting hot air. The starting port of the rear section is the fourth port of the first four-way valve, and the terminal port is connected to the second port of the bidirectional throttling device, which is the connection port of the far end of the refrigerant passage of the second evaporator. The fourth port of the second four-way valve is reserved for the compressor return gas pipeline of the heat pump heating cycle. The throttling bypass is a special throttling bypass added to avoid the additional refrigerant flow resistance generated by the bidirectional throttling device when the heat pump resumes normal heating or cooling cycle. The bypass is in a closed state during defrost mode because the first four-way valve is in the defrost mode position, and its second and fourth ports are not connected. Refrigerant flow between the two evaporators must pass through the bidirectional throttling device. The bypass is in a connected state during normal heating or cooling mode because the first four-way valve is in the normal mode position, and its second and fourth ports are connected, thus connecting the bypass. The bypass pipe diameter is larger than the capillary throttling device. When the bypass is connected, refrigerant flow between the two evaporators will automatically select the bypass, resulting in low flow resistance.

2. The air source heat pump zoned hot gas bypass defrosting method according to claim 1, characterized in that: The aforementioned zoned hot air defrosting circuit is connected to the refrigerant circulation circuit of the three types of air source heat pumps via the third port of the first four-way valve and the first and fourth ports of the second four-way valve. Specifically, the third port of the first four-way valve is connected to the refrigerant inlet of the condenser of the single-function heating unit of the air source heat pump, or to the first port of the third four-way valve of the refrigerant circuit of the dual-function heating and cooling unit and the triple-function heating, cooling, and hot water unit of the air source heat pump; the first port of the second four-way valve is connected to the condenser of the heat pump heating cycle. The outlet of the heating throttling circuit, which is equipped with a throttling valve and a check valve, is connected to the refrigeration throttling valve in the cooling throttling circuit when connecting to a dual-purpose air-source heat pump unit. The fourth port of the second four-way valve is connected to the compressor return gas line. For a single-purpose air-source heat pump unit, the return gas line is directly connected to the gas-liquid separator inlet. For dual-purpose air-source heat pump units and triple-purpose air-source heat pump units, the return gas line is first connected to the third port of the third four-way valve, then connected to the gas-liquid separator inlet via a connecting pipe, and finally connected to the compressor inlet.

3. The air source heat pump zoned hot gas bypass defrosting method according to claim 1, characterized in that: The first and second evaporators of the partitioned hot air defrosting circuit are either the first and second evaporators of a single air source heat pump divided into two zones, or the evaporators of two air source heat pumps, A and B. A partitioned hot air defrosting circuit and its control system are shared and connected to the heating units of two independently circulating air source heat pumps (A and B), or to a dual-purpose heating and cooling unit, enabling mutual defrosting and combined cooling and heating for the two A and B air source heat pumps. This shared approach... A single-use air source heat pump with mutual defrosting, or a dual-use air source heat pump with mutual defrosting for both heating and cooling, whether composed of one or two heat pumps, is referred to as a single-use air source heat pump with mutual defrosting for heating or a dual-use air source heat pump with mutual defrosting for heating, and is collectively referred to as a mutual defrosting air source heat pump unit. The mutual defrosting air source heat pump unit is a set of partitioned hot gas defrosting circuits. The first port of the first four-way valve is connected only to the compressor exhaust port of air source heat pump A. Its third interface is only connected to the condenser refrigeration passage inlet of the heating unit of air source heat pump A, or the first interface of the third four-way valve of the dual-purpose air source heat pump A; the first interface of the second four-way valve of the partitioned hot gas defrosting circuit is connected to the heating throttling passage outlet of the heating circulation circuit of the two sets of A and B air source heat pumps, which is equipped with throttling valves and their one-way valves, or when connecting to the dual-purpose air source heat pump heating and cooling unit, it is also connected to the inlet of the refrigeration throttling valve of the refrigeration throttling passage; the fourth interface of the second four-way valve of the partitioned hot gas defrosting circuit is connected to the compressor return gas pipeline of the two sets of A and B air source heat pumps in two separate paths; during the defrosting period, only the compressor equipped with the partitioned hot gas defrosting circuit mechanism operates, and the other compressor stops operating. After defrosting, the two sets of air source heat pumps resume normal operation; the water circuits of the condensers of the two sets of A and B air source heat pumps can be connected in series or in parallel, and are equipped with hot water pumps.

4. The air source heat pump zoned hot gas bypass defrosting method according to claim 3, characterized in that: The aforementioned mutually defrosting air source heat pump unit utilizes only one set of zoned hot gas defrosting circuits and its control system, consisting of two first and second four-way valves, in conjunction with one set of air source heat pump third four-way valves, or with the switching control of the third and fourth four-way valves of two sets of A and B air source heat pumps. This enables the combined heating, defrosting of the first and second evaporators, and switching between combined cooling modes. The following control method describes the control method for a mutually defrosting air source heat pump with two sets of A and B air source heat pumps. The specific control method is as follows: (1) Heating mode: The first four-way valve is in the normal position, with its first and third ports connected and its second and fourth ports connected; the second four-way valve is in the first defrost position (position A), with its first and second ports connected and its third and fourth ports connected; the third and fourth four-way valves of heat pumps A and B are in the heating position, with their first and second ports connected, the second port connected to the refrigerant inlet of the condenser, and the third and fourth ports connected; compressors A and B are running, the water pumps or fans of condensers A and B are running, and the fans of evaporators A and B are running. (2) In the first evaporator defrost mode, the first four-way valve is in the defrost position, with its first and second ports connected and its third and fourth ports connected; the second four-way valve is in the first defrost position at position A, with its first and second ports connected and its third and fourth ports connected; the third four-way valve of heat pump A is in the heating position, with its first and second ports connected, its second port connected to the refrigerant passage inlet of the condenser, and its third and fourth ports connected; during defrost, compressor A runs and compressor B stops running; the water pumps or fans of condensers A and B stop running, the fan of evaporator B runs, and the fan of evaporator A stops running; (3) Second evaporator defrosting mode: First four-way valve is in defrost position, with its first and second ports connected and its third and fourth ports connected; Second four-way valve is in the second defrost position (B position), with its first and third ports connected and its second and fourth ports connected; Third four-way valve of heat pump A is in heating position, with its first and second ports connected, its second port connected to the refrigerant inlet of the condenser, and its third and fourth ports connected; During defrosting, compressor A runs and compressor B stops running; Water pumps or fans of condensers A and B stop running, fan of evaporator A runs and fan of evaporator B stops running; After defrosting, heat pumps A and B resume normal heating mode; (4) Cooling mode: only for air source heat pump dual-purpose cooling and heating units and air source heat pump triple-purpose cooling, heating and hot water units. The first four-way valve is in the normal position, with its first and third ports connected and its second and fourth ports connected; the second four-way valve is in the second defrost position (B position), with its first and third ports connected and its second and fourth ports connected; the third and fourth four-way valves of heat pumps A and B are in the cooling position, with their first and third ports connected and their second and fourth ports connected; heat pumps A and B are running simultaneously; the water pumps or fans of condensers A and B are running; and the fans of evaporators A and B are running.

5. The air source heat pump zoned hot gas bypass defrosting method according to claim 3, characterized in that: The aforementioned assisted defrosting air source heat pump's single-unit heating unit, namely the zoned hot gas defrosting circuit and its control system, is connected to the single-unit heating unit of the air source heat pump. It is an air source heat pump water heater or an air source heat pump fan unit, and can execute three operating modes: normal heating cycle, and sequential defrosting cycle of the first and second evaporators. The three operating modes are: (1) When the normal heating mode is executed, the first four-way valve is in the normal position and the second four-way valve is in position A. The refrigerant circulation process is as follows: compressors A and B, the exhaust of compressor A passes through the first four-way valve through the first and third interface passages, condensers A and B release heat, throttling valves A and B, check valves A and B, the first four-way valve through the first and second interface passages, the first evaporator, the throttling bypass front section and its bypass check valve, the first four-way valve through the second and fourth interface passages, the throttling bypass rear section, the second evaporator, the second four-way valve through the third and fourth interface passages, gas-liquid separators A and B, compressors A and B; (2) Execute the first evaporator defrost mode, the first four-way valve is in the defrost position, and the second four-way valve is in position A; the refrigerant circulation process is as follows: A compressor, the first four-way valve 1 and 2 interface passages, hot gas check valve, the second four-way valve 1 and 2 interface passages, the first evaporator defrost, the bidirectional throttle, the second evaporator heat absorption, the second four-way valve 3 and 4 interface passages, A gas-liquid separator, A compressor; (3) Execute the second evaporator defrost mode, with the first four-way valve in the defrost position and the second four-way valve in position B; the refrigerant circulation process is as follows: A compressor, the first four-way valve's first and second interface passages, hot gas check valve, the second four-way valve's first and third interface passages, the second evaporator defrost, the bidirectional throttle, the first evaporator heat absorption, the second four-way valve's second and fourth interface passages, A gas-liquid separator, A compressor.

6. The air source heat pump zoned hot gas bypass defrosting method according to claim 3, characterized in that: The aforementioned assisted defrosting air source heat pump dual-purpose unit, namely the zoned hot air defrosting circuit and its control system, is connected to the air source heat pump heating and cooling dual-purpose unit. It is either an assisted defrosting air source heat pump water heater or an assisted defrosting air source heat pump fan unit, and can execute four operating modes: normal heating and cooling cycles, and sequential defrosting cycles of the first and second evaporators. The four operating modes are as follows: (1) When the normal heating mode is executed, the first four-way valve is in the normal position and the second four-way valve is in position A; the third and fourth four-way valves of heat pumps A and B are in the heating mode position; the refrigerant circulation process of heat pumps A and B is as follows: A and B compressors, refrigerant of heat pump A through the first four-way valve through the first four-way valve through the first and third interfaces, the third and fourth four-way valves of heat pumps A and B through the first and second interfaces, A and B condensers release heat, A and B heating throttling valves, A and B one-way valves, the second four-way valve through the first and second interfaces, the first evaporator absorbs heat, the bypass one-way valve, the first section of the throttling bypass, the first four-way valve through the second and fourth interfaces, the second section of the throttling bypass, the second evaporator absorbs heat, the second four-way valve through the third and fourth interfaces, the third and fourth four-way valves of heat pumps A and B through the third and fourth interfaces, A and B gas-liquid separators, A and B compressors; (2) When the normal cooling mode is executed, the first four-way valve is in the normal position, the second four-way valve is in the B position of the second evaporator defrost position, and the third and fourth four-way valves of heat pumps A and B are in the cooling position; the refrigerant circulation process of heat pumps A and B is as follows: A and B compressors, the refrigerant of heat pump A passes through the first four-way valve through the first four-way valve through the first and third interfaces, the third and fourth four-way valves of heat pumps A and B through the first and third interfaces, the second four-way valve through the fourth and second interfaces, the first evaporator acts as a condenser to release heat, the bypass check valve, the first section of the throttling bypass, the first four-way valve through the second and fourth interfaces, the second section of the throttling bypass, the second evaporator acts as a condenser to release heat, the second four-way valve through the third and first interfaces, the A and B cooling throttling valves, the A and B cooling check valves, the A and B condensers act as evaporators to absorb heat and produce chilled water, the third and fourth four-way valves of heat pumps through the second and fourth interfaces, the A and B gas-liquid separators, and the A and B compressors; (3) When the first evaporator defrost mode is executed, the first four-way valve is in the defrost position, the second four-way valve is in position A, and the third four-way valve is in the normal position. The refrigerant circulation process is as follows: A compressor, first four-way valve 1 and 2 interface passages, hot gas check valve, second four-way valve 1 and 2 interface passages, first evaporator defrost, bidirectional throttle, second evaporator heat absorption, second four-way valve 3 and 4 interface passages, A third four-way valve 3 and 4 interface passages, A gas-liquid separator, A compressor; (4) When the second evaporator defrost mode is executed, the first four-way valve is in the defrost mode position, the second four-way valve is in position B, and the third four-way valve is in the normal position; The refrigerant cycle is as follows: Compressor A, first four-way valve, ports 1 and 2, hot gas check valve, second four-way valve, ports 1 and 3, second evaporator defrosting, bidirectional throttling device, first evaporator heat absorption, second four-way valve, ports 2 and 4, third four-way valve, ports 3 and 4, gas-liquid separator A, compressor A.

7. The air source heat pump zoned hot gas bypass defrosting method according to claim 3, characterized in that: When the first and second evaporators of the air source heat pump with mutual defrosting are arranged vertically, the first evaporator that defrosts first is arranged on top, and the second evaporator that defrosts later is arranged on the bottom. The evaporators arranged side by side with top blowing are designated as the first evaporator, which is the evaporator that houses the main components of the zoned hot gas defrosting circuit. The air source water source heat pump water heater to which the zoned hot gas defrosting circuit and its control system are connected has its air evaporator installed independently outdoors, while the water evaporator, condenser, compressor, and control system are all installed indoors.

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